Conventionally, in an electronic computer of high versatility, such as a personal computer, when the electronic computer is to be activated to perform jobs, after the main power source is turned on, an initial start-up job starts so that the electronic computer executes a preset start-up program and reads files necessary for the start-up into the main storage of the electronic computer to enter a usable state.
More specifically, of a large number of files stored in an auxiliary storage, such as a hard disk, files necessary for the start-up are read into a main memory serving as the main storage of the electronic computer and further into a cache memory of a system LSI chip to thereby allow a necessary input to be acknowledged and complete the initial start-up job.
Since the initial start-up job is influenced by the processing speed of the electronic computer, it generally takes about several tens seconds to several minutes.
When a shut-down operation of the electronic computer is performed after the completion of jobs, the electronic computer does not turn off the main power source at once, but an operation halt job starts to terminate a job of a running program, if any, and after the program is terminated, to write information of a file used by the program into a hard disk and to allow the main power source to be turned off after it is confirmed that the state of the electronic computer permits turn-off of the main power source.
This operation halt job is also influenced by the processing speed of the electronic computer, so that it takes at least about several seconds to several tens seconds.
The operation halt job is performed in order to make it easy to generate the start-up state for the next start-up and to specify the initial start-up state in which only a minimum of programs necessary for the next start-up are activated. On the other hand, the initial start-up job is configured to start up the electronic computer smoothly by performing a start-up process in accordance with initial start-up state information for the next start-up specified by the preceding operation halt job.
However, since information stored in respective storage circuits, such as registers, latches, flip-flop's and counters, in a system LSI chip, which is the central processing unit of the electronic computer, is not necessary as the initial start-up state information for the next start-up, the operation halt job does not store this information as a file in a hard disk. Moreover, since each storage circuit, such as a register, a latch, a flip-flop and a counter is volatile, the information stored in each storage circuit is extinguished upon stopping of power feeding to the system LSI chip.
Instead of a normal shut-down operation, if a power failure occurs or a plug of the electronic computer is erroneously pulled out of an outlet and power feeding is stopped during the operation of the electronic computer, each device constituting the electronic computer is stopped at once so that a system-down occurs.
A means for storing information stored when the system-down occurs in volatile storage circuits, such as registers, latches, flip-flop's and counters in the electronic computer, particularly in the system LSI chip, is not presently provided. Therefore, if the system-down occurs, the information of a job status in the electronic computer before occurrence of the system-down is extinguished.
In order to prevent the loss of the job state information by the system-down, the electronic computer automatically and periodically forms back-up files of the files used by jobs and stores the back-up files in a hard disk. When the system-down occurs and after the electronic computer is restarted, the latest back-up files are read so that the state approximate to the state when the system-down occurred can be recovered.
When the system-down occurs, the electronic computer is stopped without executing the operation halt job. Therefore, the initial start-up state for the next start-up cannot be specified and a smooth next start-up is hindered. Also, in this case, by using proper back-up files, for example, the initial start-up state information for the preceding start-up, a smooth restart can be executed.
However, the conventional electronic computer described above cannot realize an instant-on function of reproducing the preceding use state immediately after the main power source is turned on and an instant-off function of turning off the main power source immediately after the shut-down operation. There arises, therefore, the problem that it takes a very long time to perform the start-up and shut-down operations.
Similarly, when the power source is turned off by a power failure or the like, information stored in storage circuits, such as registers, latches, flip-flop's and counters in the system LSI chip, is not held. This results in the problem that it is not possible to make the electronic computer perfectly recover the state immediately before turn-off, after the restart followed by the system-down.
The above-described problems can be solved by using non-volatile storage circuits capable of maintaining storage information even after stopping power feeding, as the storage circuit, such as registers, latches, flip-flops and counters in the system LSI. However, if registers, latches, flip-flop's and counters are constituted of non-volatile storage circuits, as practical problems, operations such as information write to the storage circuits and information read from the storage circuits are slower than when the volatile storage circuits are used, and a power consumption is larger than that of the volatile storage circuits. Therefore, if the system LSI chip is constituted of non-volatile storage circuits, there arises the problem that it is difficult to improve the performance of the system LSI chip.